The present invention relates to a method of controlling the attitude of a boat at high speed through boat hull design, and a boat hull constructed in accordance with the teachings of the method.
It is generally accepted practice that the optimum attack angle of a powered planning hull to the water surface is approximately 2.5xc2x0 to 3.0xc2x0. It has been found, however, that it is difficult to maintain an attack angle of between 2 and 3 degrees as a motor boat accelerates. This is particularly the case with motor boats powered by inboard jets, as the thrust line is higher than with motor boats powered by outboard motors. A lower thrust line allows greater leverage on the hull when trimming the drive to achieve the desired ride angle of the boat. The high thrust line of the jet is not nearly as effective in this regard because as the speed of a jet boat increases, hydrodynamic pressure builds near the stern making it difficult to maintain an effective planing attitude. This results in the hull running flat which creates a greater wetted surface area. The greater the wetted surface area of the hull, the more frictional water drag occurs resulting in poor handling and a loss of control of the boat.
What is required is a method of controlling the attitude of a boat at high speed through boat hull design, and a boat hull constructed in accordance with the teachings of the method.
According to one aspect of the present invention there is provided a method of controlling the attitude of a boat at high speed through boat hull design. A first step involves forming a pair of high speed steps in the hull of the boat adjacent to the stern on opposite sides of the keel between the chines to control the attitude of the boat at high speed. The length of the pair of high speed steps must be not less than 10% and not more than 30% of the length of the hull. The width of the each of the pair of high speed steps must be not less than 20% and not more than 40% of the chine to chine width of the hull. The depth of the each of the pair of high speed steps must be not less than 1% and not more than 5% of the chine to chine width of the hull. A second step involves forming at least one pair of transition steps in the hull of the boat adjacent to the pair of high speed steps on opposite sides of the keel and between the chines to provide a transition to the pair of high speed steps. The length of the pair of transition steps is not less than 10% and not more than 30% of the length of the hull. The width of the each of the pair of transition steps is not less than 20% and not more than 40% of the chine to chine width of the hull. The depth of the each of the at least one pair of transition steps being not less than 0.5% and not more than 2.5% of the chine to chine width of the hull.
According to another aspect of the present invention there is provided a boat hull that is constructed in accordance with the teachings of the present method.
With a boat hull constructed in accordance with the teachings of the above method, the wetted surface area of the boat is less at high speed, as will hereinafter be further described. This method also aids in turning and lifting of the hull by trapping air and water in the steps.